Forward Optical Scattering from Very Rough Surfaces Near Grazing Incidence

摘要

A series of metal and dielectric targets exhibiting fractal characteristics areproduced having a range of surface roughnesses between about 1 and 16. They are all sufficiently rough that only diffuse reflection was obtained from them when illuminated with a He-Ne laser beam. The intensity scattered in the specular direction has been measured as a function of the surface roughness for near normal theta sub 20 deg and near grazing theta sub 85 deg incidence. The specular direction intensity at first falls rapidly with increasing surface roughness, but then saturates at high values of the surface roughness. Good agreement is obtained between the experimentally observed variation with surface roughness and that predicted theoretically using a fractal surface scattering models and surface parameters measured using a profile instrument. A simple graphical model is used to demonstrate qualitatively the trends observed.